The design life of a component or product is the period of time during which the item is expected by its designers to work within its specified parameters; in other words, the life expectancy of the item. It is the length of time between placement into service of a single item and that items on-set of wear-out.
The design life of components and products differs from the items mean time between failure (MTBF), in that MTBF is a measure of the rate of occurrence of random failures in time where these failures are not due to a wear-out mechanism. For example, the MTBF of a device may be 100,000 hours and the design-life is 20,000 hours. In this example, across the population of products, one failure will occur, on average, every 100,000 population operating hours (100,000 units operating for 1 hour each = 100,000 population operating hours). None of these units will ever approach reaching 100,000 operating hours as it will fail due to wear-out and be replaced by a new unit. Aluminum electrolytic capacitors, fans, and batteries are classic examples of components that will fail due to wear-out well before they could achieve the operating time indicated by their individual MTBF.
Another use of the term design-life deals with consumer products. Many products employ design-life as one factor of their differentiation from competing products and components. A disposable camera is designed to withstand a short life, whilst an expensive single-lens reflex camera can be expected to have a design life measured in years or decades. (Clearly in this example there are other differentiators).
Read more about Design Life: Long Design Lives, Short Design Lives, Obsolescence
Famous quotes containing the words design and/or life:
“For I choose that my remembrances of him should be pleasing, affecting, religious. I will love him as a glorified friend, after the free way of friendship, and not pay him a stiff sign of respect, as men do to those whom they fear. A passage read from his discourses, a moving provocation to works like his, any act or meeting which tends to awaken a pure thought, a flow of love, an original design of virtue, I call a worthy, a true commemoration.”
—Ralph Waldo Emerson (1803–1882)
“Just as we need to encourage women to test life’s many options, we need to acknowledge real limits of energy and resources. It would be pointless and cruel to prescribe role combination for every woman at each moment of her life. Life has its seasons. There are moments when a woman ought to invest emotionally in many different roles, and other moments when she may need to conserve her psychological energies.”
—Faye J. Crosby (20th century)